Stent configurations

ABSTRACT

Improved stent configurations exhibiting limited recoil, resistance to compression and improved longitudinal flexibility are disclosed. The stent comprised of a plurality of annular elements aligned to form a cylindrical stent body. The annular elements are comprised of a plurality of open, generally boomerang-shaped segments interconnected top-to-bottom around each of the annular elements. Adjacent annular elements are interconnected by interconnecting element.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] This invention relates to stents of improved configuration.

[0003] 2. Brief Description of the Prior Art

[0004] Stents are radially expandable endoprosthesis which are typicallyintravascular implants capable of being implanted transluminally andenlarged radially after being introduced percutaneously. They have alsobeen implanted in urinary tracts and bile ducts. They are used toreinforce body vessels and to prevent restenosis following angioplastyin the vascular system. They may be self-expanding or expanded by aninternal radial force, such as when mounted on a balloon.

[0005] In the past, stents have been generally tubular but have beencomposed of many configurations and have been made of many materials,including metals and plastic. Ordinary metals such as stainless steelhave been used as have shape memory metals such as Nitinol and the like.Stents have also been made of biodegradable plastic materials. Suchstents have been formed from wire, tube stock, etc. Some stents areself-expanding and some are expanded by an interior radial force.

SUMMARY OF THE INVENTION

[0006] This invention provides new configurations of the segments makingup stents which may be adapted to all of the various types of prior artstents described above and/or known previously in the art. There arenumerous advantages to the new configurations. For example, theconfigurations of the invention limit recoil and add resistance tocompression for an expanded stent, among other things. Also, the stentsof this invention are longitudinally flexible.

[0007] The inventive stents comprise a plurality of annular elementsaligned to form a cylindrical stent body. Each annular element, in turn,is comprised of a plurality of open, generally boomerang-shapedsegments. The segments are interconnected top-to-bottom around each ofthe annular elements. Adjacent annular elements are interconnected byone or more interconnecting elements. Each interconnecting elementextends from an end of a boomerang-shaped segment in one annular elementto an end of a boomerang-shaped segment in an adjacent annular element.In a preferred embodiment an interconnecting element extends from eachboomerang-shaped segment in an annular element to a neighboringboomerang-shaped segment in an adjacent annular element.

[0008] Interconnecting elements joining adjacent annular elements aredesirably U-shaped or zig-zag shaped, although other curvilinear andrectilinear interconnecting elements may also be used.

[0009] Adjacent boomerang-shaped segments in an annular element may beinterconnected via a link extending from the top of a segment to thebottom of an adjacent segment. The links may range in design from ashort, straight connector to any of the shapes described below for theinterconnecting elements.

BRIEF DESCRIPTION OF THE FIGURES

[0010]FIG. 1 is a schematic showing boomerang shapes;

[0011]FIG. 2 is a flat plan view of an embodiment of a stentconfiguration of the invention in the unexpanded condition;

[0012]FIG. 3 is a longitudinal view of the stent of FIG. 2 in its normaltubular unexpanded condition;

[0013]FIG. 4 is a flat plan view of an embodiment of a stentconfiguration of the invention in the unexpanded condition;

[0014]FIG. 5 is a longitudinal view of the stent of FIG. 3 in itstubular, expanded condition;

[0015]FIG. 6 is an interconnecting element that may be used to joinadjacent annular elements in another embodiment of the invention; and

[0016]FIG. 7 is a view of the stent of FIG. 3 after being bent.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0017] For the purposes of this invention, the term boomerang is used todescribe the shape of certain stent segments and is used in the sense asdescribed in the Websters New Collegiate Dictionary with reference toFIG. 1 hereof:

[0018] “boomerang 1: A bent or angular throwing club which can be thrownso as to return near the starting point.”

[0019] An embodiment of a generally cylindrical stent according to theinvention is illustrated in the flat at 110 in FIG. 2 or FIG. 4. Thestent may be formed of a metal tube such as nitinol, or stainless steelpreferably, which has been etched or preferably laser cut to theconfiguration shown in the flat plan view of FIG. 2 or 4. Theconfiguration may be formed in flat sheet and rolled into a cylinderwith a welded seam or the like joining together edges 112 and 114, orthe configuration may be formed directly in a small tube such as ahypotube. A tubular form of the stent is shown generally at 210 in FIG.3.

[0020] The configurations shown in FIGS. 2-4 are made up of a pluralityof aligned annular elements 114 aligned as shown to provide a generallycylindrical stent body. Each annular element 114 is comprised of aseries of generally boomerang shaped segments indicated at 118 (seedarkened segment in the Figures for clarity) having an open structurejoined top 120 to bottom 122 at segment junction 124. Segments 118 arearranged or networked as shown in the Figures with ends 126 ofneighboring segments on adjacent annular elements joined byinterconnecting elements 128. In FIGS. 2-4, interconnecting element 128is a U-shaped element which is a partly open curve. Alternativeinterconnecting elements including zig-zag shaped element 228 as shownin FIG. 6, which may be used in place of U-shaped element 128 to joinadjacent annular elements 114 together.

[0021] The configurations of FIGS. 2 and 4 are substantially similar toone another, differing principally in the presence of a dimple 130 ineach bottom 122 of each segment 118 in the configuration of FIG. 4.Without being bound by a particular theory, it is believed that thepresence of the dimple limits the extent to which the stent buckles outof the plane on expansion.

[0022] It is desirable that the boomerang-shaped segments be at leastsubstantially symmetric about a midline 138 extending from the top 120of the segment to the bottom 122 of the segment. Midline 138 is situatedmidway between ends 126 of the segment.

[0023] When the stent of FIG. 2 is expanded, as shown generally at 310in FIG. 5 on a balloon for example, the boomerang-shaped segments 118 ofthe unexpanded stent take on a new configuration. The segments 318 takeon the shape of rounded triangles with bulging bottoms 322.

[0024] It is desirable that the interconnecting elements be U-shaped asshown in FIGS. 2 and 4 or zig-zag shaped as shown in FIG. 6. However, ina more general sense, the invention contemplates the use of curvilinearas well as rectilinear interconnecting elements, including straightelements. Examples of other suitable connectors are disclosed in U.S.patent application Ser. No. 09/111,531 filed Jul. 8, 1998, U.S. patentapplication Ser. No. 08/846,164 filed Apr. 25, 1997, WO 97/32543 toDivysio Solutions LTD. and WO 97/40780 to David G. Jang, all of whichare incorporated herein by reference. Of course, adjacentboomerang-shaped segments may also be joined side-by-side with a regionof overlap between adjacent boomerang-shaped segments.

[0025] It is also desirable that interconnecting elements be flexible soas to accommodate bending of the stent without substantial distortion ofthe boomerang-shaped segments. FIG. 7 shows the stent of FIG. 3 havingbeen bent. As shown in FIG. 7, as the stent is bent, interconnectingelements in tension open while interconnecting elements in compressionclose to accommodate bending of the stent.

[0026] Although as shown in the Figures an interconnecting elementextends from each boomerang-shaped segment in an annular element to anearest neighboring boomerang-shaped segment in an adjacent annularelement, the invention further contemplates the possibility of aninterconnecting element extending from each boomerang-shaped segment inan annular element to a next-nearest neighboring boomerang-shapedsegment in an adjacent annular element. In the latter case, the firstend 140 and second end 144 of each interconnecting element 128 would becircumferentially offset along the stent.

[0027] In a more general sense, the invention further contemplates astent in which each adjacent annular element is interconnected by one ormore interconnecting elements and each interconnecting element extendsfrom an end of a boomerang-shaped segment in one annular element to anend of a boomerang-shaped segment in an adjacent annular element. Assuch, an interconnecting element need not extend from eachboomerang-shaped segment. An example of this is a stent in whichinterconnecting elements extend from every second or thirdboomerang-shaped segment in an annular element.

[0028] The invention also contemplates the possibility of altering theorientation of some of the annular elements. In one such embodiment,adjacent annular elements in the flat pattern are rotated by 180°relative to one another so that adjacent annular elements point inopposite directions.

[0029] Although the ends of nearest neighboring segments in adjacentannular elements are shown in the figures as aligned with one anotheralong the circumference of the stent, the invention further contemplatesembodiments of the stent in which nearest neighboring segments inadjacent annular elements are circumferentially displaced relative toone another.

[0030] In yet another series of embodiments, adjacent (or non-adjacent)annular elements may be formed of different sized boomerang-shapedelements. As such, adjacent (or non-adjacent) annular elements may spandifferent lengths. Alternatively, adjacent (or non-adjacent) annularelements may comprise different numbers of boomerang-shaped segments.

[0031] Although in the embodiment of FIGS. 2-4, segment junction 124 isshown as a small, straight link extending from the top of one segment tothe bottom of an adjacent segment, the invention also contemplates thepossibility of adjacent boomerang-shaped segments within an annularelement being connected by U shaped links, zig-zag shaped links or anyof the shapes disclosed above for the interconnecting elements.Additionally, other shaped segments may be interspersed among theboomerang-shaped segments.

[0032] The inventive stent may be self-expanding or mechanicallyexpandable such as by balloon. The stent may be made of a variety ofsuitable bio-compatible materials including metal, plastic and any othermaterial capable of functioning as an expandable stent. For example, thestent may be of metal wire or ribbon such as tantalum, stainless steelor the like or of metal sheeting or metal tubing. It may be thin-walled.It may be of shape memory alloy such as Nitinol or the like.

[0033] The above Examples and disclosure are intended to be illustrativeand not exhaustive. These examples and description will suggest manyvariations and alternatives to one of ordinary skill in this art. Allthese alternatives and variations are intended to be included within thescope of the attached claims. Those familiar with the art may recognizeother equivalents to the specific embodiments described herein whichequivalents are also intended to be encompassed by the claims attachedhereto.

What is claimed is as follows:
 1. A generally cylindrical, radiallyexpandable stent comprised of a plurality of annular elements aligned toform a cylindrical stent body, each element comprised of a plurality ofopen, boomerang-shaped segments, each segment having a top and a bottom,the segments interconnected top-to-bottom around each of the annularelements, adjacent annular elements interconnected in one or moreplaces.
 2. The stent of claim 1 wherein adjacent annular elements areinterconnected by one or more interconnecting elements, eachinterconnecting element extending from an end of a boomerang-shapedsegment in one annular element to an end of a boomerang-shaped segmentin an adjacent annular element.
 3. The stent of claim 1 wherein aninterconnecting element extends from each boomerang-shaped segment in anannular element to a boomerang-shaped segment in an adjacent annularelement.
 4. The stent of claim 3 wherein an interconnecting elementextends from each boomerang-shaped segment in an annular element to aneighboring boomerang-shaped segment in an adjacent annular element. 5.The stent of claim 1 wherein each interconnecting element has one ormore bends therein.
 6. The stent of claim 5 wherein each interconnectingelement is a U-shaped segment.
 7. The stent of claim 5 wherein eachinterconnecting element is a zig-zag-shaped segment.
 8. The stent ofclaim 1 wherein at least a portion of each interconnecting element iscurvilinear
 9. The stent of claim 1 wherein each boomerang-shapedsegment is symmetric about a midline extending from the top of thesegment to the bottom of the segment, the midline situated midwaybetween the ends of the segments
 10. The stent of claim 1 wherein eachbottom has a dimple therein.
 11. The stent of claim 1 made of metal. 12.The stent of claim 11 made of stainless steel.
 13. The stent of claim 11wherein the metal is a shape memory metal.
 14. The stent of claim 1 madeof a bio-compatible material.
 15. A generally cylindrical, radiallyexpandable stent comprised of a plurality of annular elements aligned toform a cylindrical stent body, each element comprised of a plurality ofopen, boomerang-shaped segments interconnected top-to-bottom around eachof the annular elements, and interconnecting U-shaped elementsinterconnecting adjacent ends of each boomerang-shaped segment to aneighboring segment in an adjacent annular element.
 16. A generallycylindrical, radially expandable stent comprised of a plurality ofannular elements aligned to form a cylindrical stent body, each elementcomprised of a plurality of open, boomerang-shaped segments, eachsegment having a top and a bottom, adjacent segments in an annularelement connected by a link extending from the top of a segment to thebottom of an adjacent segment, adjacent annular elements interconnectedby one or more interconnecting elements, each interconnecting elementextending from an end of a boomerang-shaped segment in one annularelement to an end of a boomerang-shaped segment in an adjacent annularelement.